Problem Reading DVD data

Whenever I try to read data from DVD to install games or softweres, the system become slow or sometime the screen freezed. I'm quite sure it's not the disk problem as I have went back to the seller and he have tested in his computer, it perfectly alright. He said I should try to copy the setup file into my computer as the problem lie in the laptop ram. I did that and after the meter run for awhile it prompt me with the message invalid MS-DOS function.

By the way I'm using PHILIPS CDRW/DVD SCB5265...

Please help...

just to add on.. it's just strange that, my drive are able to display the files in the disk, it's only when reading, processing the file where the problem come, the computer lock up and process very slowly and take ages to respond...